Process of making negatives in metal of solid objects or surfaces



Oct. 7, 1941. H. s. INGHAM ETAL 2,258,452

PROCESS OF MAKING NEGATIVES IN METAL OF SOLID OBJECTS OR SURFACES FiledJan. 31, 1940 4 Y 42 wi w m ama Y fl B 4 Patented Oct. 7, 1941 PROCESSOF MAKING NEGATIVES IN METAL OF SOLID OBJECTS OR SURFACES Herbert S.Ingham,

New Jersey Jamaica, and Arthur P. Shepard, Forest Hills, Long Island, N.Y., assignbrs to Metallizing Engineering Company, Inc., Long IslandCity, N. Y., a corporation of Application January 31, 1940, Serial No.316,583

Claims.

This invention relates to a new and useful process of making negativesin metal of solid objects or surfaces.

One object of the invention comprises, inter alia, the making, by metalspraying, of substantially accurate negatives or molds and reproductionsor replicas in metal of solid objects or surfaces and this and otherobjects will be seen from the following description.

The application of metal coatings to solid'objects or surfaces by metalspraying is achieved by the use of a metal spray gun, i. e., a device bywhich metal is fed to a heating zone from which zone metal particles, atleast some of which are molten or in a heat plastic condition, arepropelled against the object or surface by a blast of air or other gas.Various types of spray guns are commonly used for this-purpose. In orderto obtain a substantially coherent coating on the object or surfacesprayed, it is essential that the metal particles, as they impinge uponthe surface sprayed, enter into a bond with such surface to a sumcientextent to permit the formation of a satisfactory coating thereon. If thebond between the impinging metal particles and the surface sprayed isnot sufficient for the formation of a substantially coherent metalcoating, the spray metal will not adhere to such surface and is eitherblown off by the force of the blast from the spray gun or, if it formsflakes upon the surface sprayed, these flakes curl, thus preventing theformation of the desired coating. In such cases it is necessary toprovide for the requisite degree of bonding between the impinging metalparticles and the surface sprayed by the use of suitable methods. Thesurface to be sprayed may thus be pre-treated, for instance, by sandblasting, grit blasting, machining, acid etching or the like to renderthe same rough or porous.

For the procurement of detachable spray metal coatings it is requisitethat the spray metal be applied to the surface sprayed in a thickness atleast sufficient to yield a substantially self-supporting spray metalshell structure. Spray metal coatings of such thickness, however, have atendency to peel at the edges, thus resulting in warpage of the spraymetal structure and inaccuracy of the negative surfaces obtained. Thehigher, however, the degree of bonding between the impinging spray metalparticles and the surface sprayed, the lower will this tendency to peelmanifest itself. Inasmuch as the making of spray metal negativesrequires the spraying of coatings that can be separated from the surfacesprayed substantially intact, i. e., substantially without injury to thecoating, it is necessary that the bond between the spray metal coatingand the surface to which it is applied be sufficiently low to permit aseverance of that bond without injury to the coating. This requirement,however, necessitates, in many cases, a bond which is insufflcientlyhigh to counteract the peeling-of the coating off the edges. I

In the making of negatives or molds and replicas or duplicates in metalof solid objects or surfaces by metal spraying, the object or surfacesprayed upon is usually called a matrix, i. e., a substantially accuratenegative of the object or surface to be obtained therefrom. If thematrix is itself a negative of a model, a model being an object orsurface desired to be reproduced, it constitutes a mold from whichreplicas or duplicates of such model can be made, whereas if the matrixis itself a positive of a model, it constitutes a so-called master (i.e., either the original of the object or surface desired to bereproduced, or, a substantially accurate replica or duplicate of suchobject or surface) from which a negative or mold may be made. Suchnegatives or molds are, for instance, produced for use in the multiplereproduction of articles in various industries and particularly in theplastics, rubber and similar industries.

We have discovered that it is possible to obtain substantially accuratespray metal negatives of a matrix by spraying in a manner which willsubstantially counter-act the tendency of the spray metal shell to peeloff the edges and which will substantially eliminate the necessity for ahigh degree of bonding between the shell andthe matrix, thus yieldingspray metal coatings that may be separated and removed from the matrixsprayed substantially without injury to the coat- In accordance with thepresent invention, the I object or surface, herein referred to as amatrix, of which a negative is to be formed, is

provided with a base member extending suba substantially coherent spraymetal shell, i. e...

a spray metal coating of at least self-supporting thickness, on thematrix and the base member and extending on the base member to the frameIf desired, the spraying may be so conducted as to first spray metal, onsubstantially all sides of the matrix, onto the base member and into thespace defined by the matrix, the base member and the frame member atleast until a substantially coherent spray metal coat is formed on thebase member and extending from the matrix to the frame member andthereafter spraying metal onto the coating thusly obtained and onto thematrix to build up the spray metal shell. It is also possible to firstspray the matrix with metal to form a spray metal fiash thereon, i. e.,a substantially coherent spray metal coating of relative thinness,whereupon metal is sprayed onto the matrix and auxiliary structures, inaccordance with the invention, or first onto the auxiliary structure andthereafter the matrix and such structure as hereinbefore set forth.

In the following a specific embodiment of our invention is set forth byway of example but not by way of limitation and the invention will bemore fully understood from the following description read in conjunctionwith the drawing in which Fig. 1 is a cross section through an articleto be reproduced;

Fig. 2 is a top view of a structure showing a frame member and a basesupported matrix in the form of a master of the article shown in Fig. 1;

Fig. 3 shows a cross section through a matrix in the form of a master ofthe article shown in Fig. 1 with a frame member on its base member andhaving a coating of applied spray metal;

Fig. 4 illustrates a cross section through the finished negative;

Fig. 5 is a cross section through a finished negative in the form of amold having a base member as a flash shearing ring; and

Fig. 6 is a cross section through a finished negative in the form of amold having a single unit base member and frame member as a fiashshearing ring,

In the drawing l designates the article to be reproduced. A matrix 2 inthe form of a substantially accurate master or duplicate of the articleI and having preferably a base portion 3 is provided with a spray metalcoating 4 applied in the manner well known in the metal spraying art toproduce a separable mold shell by means of a gas blast type spray gunschematically indicated at 5. The spray metal coating 4 fills the spacebetween the matrix 2 and a frame member 6 in the form of a ringsurrounding the matrix and resting on the base member 3 and preferablysecured thereto by such means as screws Ill. After separation of thespray metal shell from the matrix the former may be suitably machined torepresent the finished negative or mold 1 shown in Fig. 4 possessingthe' ring 6 adjacent the base of the mold body.

' The material of the matrix may be any suitable metallic ornon-metallic material provided the same lends itself to be suitablyseparated from the spray metal coating thereto applied in accordancewith well known practices. We prefer, however, to use a metal matrix.

Instead of using, as for instance'illustrated in Fig. 3, a matrix havinga suitable base member,

'as a substantially integral part thereof, it is possible and sometimesof advantage to construct the matrix without such base member and toseparately provide the matrix with any suitable object or surfaceadapted to be sprayed upon with metal. Irrespective, however, of whetherthe base member constitutes an integral part of the matrix or not, thesame should be so fitted on the matrix that it extends substantially onall sides from the matrix adjacent the surface thereof. In most cases itwill suffice to select as the base member a suitable plate or the likesurface to which the matrix as well as the frame member are fitted. Thisis particularly true where the matrix constitutes a male structure. Inmany cases where the matrix is essentially a female structure goodresults are obtained by inserting the matrix into a correspondinglycut-out portion of a suitable plate, to an extent sufiioient to bringthe outer rim of the surface of the matrix as closely as possible inalignment with the plate used as a base member.

The particular spraying technique for the building up of the spray metalshell in accordance with our invention onto and over the surface of thematrix depends to some extent upon the particular type of matrix used.If the matrix is substantially a male structure the metal spraying willordinarily proceed by building from the base member upward onto andaround the structure, whereas if the matrix is substantially a femalestructure the formation of the spray metal shell is accomplished bybuilding up the spray metal from the base member into the cavity orcavities of the structure and thus onto and over the matrix.

The base member, instead of being either a constituent part of thematrix or of being an individual separate structure, may form aconstituent part of the frame member to be suitably fitted to the matrixsubstantially as a single base member-frame member unit. It isunderstood that it is also possible to arrange the base member as wellas the frame member and matrix as a substantially single unitarystructure. The base member may be removed from the spray metal shell orleft thereon, as desired. When retaining the base member on the spraymetal shell, as for instance, when desiring to use the same as a fiashshearing member in a spray metal mold structure, it is of advantage toselect a ring-like base member of high tensile and transverse loadingstrength such as a steel ring or the like. Such flash shearing basemember is for instance illustrated in Fig. 5 in which the flashshearing, ring like base member I5 is carried by the spray metal shellIS.

The material of the frame member may be any suitable metallic ornon-metallic material. We prefer to use, however, a suitable metallicring as the frame member. The metal of the ring may be the same metal insolid form as the metal used for the preparation of the spray metalshell or may even consist of spray metal. The frame member need notnecessarily surround the matrix on all sides; it suffices in most casesif the frame member but partially surrounds the same. The frame memberneed not necessarily be one continuous member and may comprise amultiplenumber of individual members and irrespective of whether thesame are joined together or closely spaced around the matrix. Though weprefer as a matter of convenience an arrangement whereby the framemember rests upon or is fitted to the base member, this is notabsolutely essential and the frame member may be arranged or supportedin any other manner, provided the base member substantially extends atleast to the frame member with at least a portion of the frame memberextending above the surface of the base member to be sprayed.

The frame member in accordance with the invention may be removed fromthe spray metal shell or the same may be left thereon, as desired. Theremoval of the frame member may be accomplished either incident to theseparation of the spray metal shell from the matrix, or, alternatively,as a separate independent step prior or subsequent to such separation.In some cases it is of advantage to retain the, frame member as a partof the spray metal shell. This is particularly true in the case of moldswhere a metal ring-like frame member is used. We then find it ofadvantage to select a metal ring possessing a certain elasticitycombined with high tensile strength, such as a steel ring or the like.Such ring will impart to the finished mold a high degree of tensile andtransverse loading strength. The same is preferably so constructed as toform a substantially single unit with the base member; and a constituentpart of the mold shell posi- Depending upon the material of. the matrixand the material of the structural elements composing the auxiliarystructure in accordance with the invention, the separation of the'spraymetal tioned and capable to act as a flash shearing member or ring inthe molding operation of the article to be reproduced. Such basememberframe member unit is for instance illustrated in Fig. 6 in whichthis unit, as a flash shearing ring I I, is carried by the spray metalshell I2.

The surface of the matrix or of the base member or of the frame membermay be suitably treated if desired to secure a satisfactory bonding withthe impinging spray metal particles. Thus, for instance, if such surfaceconsists of a substantially smooth material, the same may be lightlysand or grit blasted and thereafter sprayed.

If the frame member or base member are desired to be obtained as aconstituent part of the finished mold shell it is of advantage tosuitably treat the same to improve the bonding with the spray metal sothat they may become as much as possible anchored to the spray metalmold shell. This may be accomplishd by heavy sand blasting, gritblasting, or the like or by otherwise heavily roughening, dove-tailingor keying the surface of the frame member or base member or both, as thecase may be, which is to be contacted by the spray metaL If theparticular surface already presents a heavily porous or rough aspectsuch pre-treatment may not materially increase its spray metal bond andwould not be necessary in such case.

The spraying of the matrix and of the auxiliary structure within ourinvention, i. e., the base member and frame member either separately oras a unit, may be carried out in accordance with wen known practices andshould be continued at least until a spray metal shell is formed on thematrix of a thickness sufficient to be capable of separation therefromas a substantially selfsupporting structure. This shell may be furtherbacked up, if desired, by either spraying with metal, or in any othersuitable manner, such as by casting a backing thereon.

shell therefrom may be effected in numerous ways. Thus, for instance,where the matrix or the elements in question comprise a metallicmaterial, the detachable spray metal shell may be for exampl formedthereon and removed therefrom in accordance with the process set forthin the U. S. patent to Wm. 0. Reid, No. 2,171,599. If the matrix orthese elements comprise a nonmetallic material, the separation from thespray metal shell may be accomplished in most cases by suitablestripping therefrom.

All of the structural elements composing the auxiliary device inaccordance with our invention should be preferably secured to each otherand in substantially fixed relation to the matrix by such suitable meansas screws, bolts or the like.

The foregoing specific description is for purposes of illustration andnot of limitation and it is therefore our intention that the inventionbe limited only by the appended claims or their,

equivalents in which we have endeavored to claim broadly all inherentnovelty.

We claim:

1. Process of making negatives in metal of a matrix by metal sprayingwhich comprises providing a matrix with a base member extendingsubstantially from the surface of said matrix adjacent all sidesthereof, at least partly surrounding said matrix in spaced relationthereto with a frame member, said frame member being positioned tosubstantially define with said matrix and said base member a space,spraying metal onto said matrix, said base member, and into said spaceat least until a spray metal shell of substantially self-supportingthickness is formed on said matrix and said base member substantiallyextending on said base member from said matrix to said frame member,tied down by the corner formed by said frame member and base member, andremoving at least that part of said shell covering said matrixsubstantially intact from said matrix.

2. Process in accordance with claim 1 in which said matrix is surroundedby said frame member on substantially all sides thereof.

3. Process of making negatives in metal of a matrix by metal sprayingwhich comprises providing a matrix with a base member extendingsubstantially from the surface of said matrix adjacent all sidesthereof, surrounding said matrix in spaced relation thereto with a'framemember, said frame member being positioned to substantially define withsaid matrix and said base member a space, providing said matrix with aflash of spray metal, thereafter spraying metal onto said matrix, saidbase member, and into said space at least until a spray metal shell ofsubstantially self-supporting thickness is formed on said matrix andsaid base member substantially extending on said base member from saidmatrix to said frame member, tied down by the corner formed by saidframe member and base member, and removing at least that part of saidshell covering said matrix substantially intact from said matrix.

4,. Process of making negatives in metal of a matrix by metal sprayingwhich comprises providing a matrix with a base member extendingsubstantially from the surface of said matrix adjacent all sidesthereof, surrounding said matrix in spaced relation thereto with a framemember,

said frame member being positioned to substantially define with saidmatrix and said base member a space, spraying metal onto said basemember and into said space at least until a substantially coherent spraymetal coat is formed on said base member and extending from the matrixto the frame member, and tied down by the corner formed by said framemember and base member, thereafter spraying metal onto said coat andsaid spray metal shell on said matrix and said base member substantiallyextending on said base member from said matrix to said frame member, andremoving at least that part of said shell covering said matrixsubstantially intact from said matrix.

5. Process according to claim 4 in which said matrix prior to sprayingmetal onto said base member and into said space is first provided with aflash of spray metal thereon.

' HERBERT S. INGHAM. ARTHUR P. SHEPARD.

